The invention comprises a novel method to produce alkyl cyanates, isocyanates, isocyanurates, and similar multifunctional cyanates, isocyanates and oligomers of multifunctional isocyanates.
A simple process for producing alkyl cyanates by reacting a metal alkoxide with cyanogen halide has been sought since at least 1895 when Hantzsch and Mai reported in Berichte, 28, 2466 (1895) that the reaction produced instead nearly quantitative yields of diethyl imidocarbonate.
Known methods of producing and isolating alkyl cyanates include the preparation of 5-alkoxyl-1,2,3,4-thiatriazoles followed by thermal decomposition according to the following graphic representation: ##STR1## This is the only known general method to prepare alkyl cyanates. However, it is a multistep reaction and the literature cautions that 5-alkoxyl-1,2,3,4-thiatriazole will explode if not handled carefully. Alternatively, one may prepare O-methyl-N-hydroxythiocarbamates which thermally decompose according to the following reaction: EQU ROC(S)NHOC(O)CH.sub.3 .fwdarw.ROCN+S+CH.sub.3 COOH+CH.sub.3 OC(O)NH.sub.2
The difficulty with this method is in the separation of the alkyl cyanate before further reaction occurs with other products of the decomposition. Loudas et al. in U.S. Pat. No. 3,733,349 and Grigat et al. in U.S. Pat. No. 3,553,244 disclose a method for producing certain halogenated alkyl cyanates, aryl cyanates, or aliphatic cyanates containing electron withdrawing substituents by the reaction between an alcohol, base and cyanogen chloride. The method is not generally applicable to use with unsubstituted alkyl hydroxy compounds since under such conditions the cyanogen chloride will react preferentially with the base. Finally it is known that certain aliphatic alcohols react successively with sodium hydride or butyl lithium and then with cyanogen chloride to produce cyanates. This known reaction has been used only for producing certain complex sterically hindered cyanates that were incapable of spontaneous isomerization. The three known products ##STR2## and (CH.sub.3).sub.3 CCH.sub.2 OCN, required the use of unusual aliphatic moieties and expensive bases.